1. Field
The present disclosure relates to a light emitting display device and a method of fabricating the same.
2. Description of the Related Technology
Of light emitting display devices, organic light emitting display devices, which are self-luminous display devices, are drawing attention as next-generation display devices due to their wide viewing angle, high contrast, and fast response time.
An organic light emitting display device includes an organic light emitting layer formed of an organic material between an anode and a cathode. When positive and negative voltages are respectively applied to these electrodes, holes from the anode move to the organic light emitting layer via a hole injection layer and a hole transport layer, and electrons from the cathode move to the organic light emitting layer via an electron injection layer and an electron transport layer. Then, the holes and the electrons recombine in the organic emitting layer. The recombination of the holes and the electrons generates excitons, and the organic light emitting layer emits light as the excitons change from an excited state to a ground state. As a result, an image is displayed.
The organic light emitting device includes a pixel defining layer having an opening that exposes the anode, and a light emitting layer is formed on the anode exposed through the opening of the pixel defining layer. The light emitting layer may be formed by printing a light emitting material on the anode exposed through the opening of the pixel defining layer by using an inkjet printing method or a nozzle printing method. A lyophilic surface treatment layer may be formed in order to improve the wettability of the light emitting material.
In order to determine whether the lyophilic property of a surface treatment layer satisfies a reference value, the surface treatment layer is typically formed on a small separate substrate, and a contact angle of a light emitting material on the surface treatment layer is measured. If the measured contact angle of the light emitting material on the surface treatment layer is, for example, 10 degrees or less, it is determined that the lyophilic property of the surface treatment layer satisfies the reference value.
However, even if it is determined that the lyophilic property of the surface treatment layer satisfies the reference value, the wettability of the light emitting material can be reduced in a process of fabricating an organic light emitting display device. This indicates that the method of measuring the contact angle of the light emitting material on the surface treatment layer on the small separate substrate fails to reflect a change in the wettability of the light emitting material due to a defect in the surface treatment layer which may occur in the process of fabricating the organic light emitting display device.